Detonator compositions



tees DETONATOR COMPOSITTONS David T. Zebree, Kingston, N. Y., assignor to Hercules Powder Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application December 31, 1956 Serial No. 631,467

19 Claims. (Cl. 522) of a detonating explosive such as pentaerythritol tetranitrate, a heat-sensitive primer charge such as diazodi nitrophenol superposed on the base charge, and a readily ignitable ignition charge capable of firing the primer charge by the heat generated. In the case of delay caps :an additional slow burning composition or delay fuse is generally included between the ignition and primer charges and exhibits such a predetermined rate of burning that the specified time interval elapses between the application of the firing current and the explosion of the primer charge. a i

This invention is concerned with new blasting initiator compositions advantageously applied as ignition charges in electric blasting caps, particularly in delay caps. The said charges are also applicable as delay fuses in certain applications.

An object of this invention is to provide new blasting initiators. Another object is to provide lead-tellurium compositions especially suitable as ignition charges in blasting caps. Another object is to provide lead-tellurium compositions especially suitable as a slow-burning charge in a delay cap. Still another object is to provide ignitable lead-tellurium compositions containing an additive comprising one or more selected materials to regulate the burning characteristics. Other aspects and objects will be apparent from the accompanying disclosure and the appended claims.

In accordance with this invention lead-tellurium compositions containing lead and tellurium in ignitable proportions are provided as blasting initiators. Further in accordance with this invention lead-tellurium compositions are provided which contain lead and tellurium in ignitable proportions and at least one additive capable of altering the burning characteristics of the composition and selected from the group of magnesium, aluminum, silicon, sulfur and phosphorus. Still in accordance with this invention a method is provided for regulating firing time of a blasting cap which comprises firing a cap containing a lead-tellurium ignition mixture and regulating the time of said firing by maintaining a sufficient amount of an additive of at least one of the group of magnesium, aluminum, silicon, sulfur and phosphorus to decrease the said firing time to a predetermined value.

Although it is within the scope of my invention to utilize any ignitable proportions of lead and tellurium in my composition, the preferred composition will contain from about 37 to 81 weight percent lead and from about,

1 9't'o 65 weight percent tellurium. The amount of addi- 2,867,517 Patented Jan. 6, 1959 tive component utilized depends upon the problem at hand, being, however, in the order of from about 0.3 up to 4.5 weight percent or higher if desired. Substantially stoichiometric proportions of lead and tellurium are employed to achieve maximum heat of reaction, which is of particular importance in the use of the composition as an ignition mixture in a delay cap in order to assure ignition of the fuse. However, other than stoichiometric proportions can be employed for that purpose when desired, particularly when an additive material is present to increase the heat of burning reaction as described hereinafter.

The following tabulation is illustrative of certain outstanding characteristics of my" compositions. Included for purpose of comparison are corresponding properties of lead-selenium ignition mixtures of the prior art, which mixtures are set forth in U. S. 1,989,729, issued February 5, 1935. The components of each composition are present in substantially stoichiometric proportions.

Table I Lead-Tellurium Lead- Selenium 1 25 mg sample in 1 inch 25 caliber bronze shell. 2 0.65 gram. Lead-tellurium compositions of this invention provide for a high ignition temperature, as illustrated, and not only provide for improved safety in handling, but also exhibit excellent series firing properties. For example, the critical firing current of a series of 30 caps which em,- ploy stoichiometric proportions of lead and tellurium as the ignition mixture is in the order of about 0.7 ampere. The average burning time for lead-tellurium ignition mixtures of this invention is reduced by about 10 to 20 percent by the presence of from about. 0.3 to 4.5 weight percent of an additive of the group of magnesium, silicon, aluminum, sulfur and phosphorus. The spread, or maximum deviation from the average burning time is reduced, by the presence of the said additive, by about 15-20 percent. Thus by way of further example a 0.7 gram stoichiometric mixture of lead and tellurium which has an average burning time of about 160 milliseconds will, in the presence of from 1 to 2 percent magnesium, have an average burning time of about 130-440 milliseconds; and a spread of about -85 milliseconds as compared with a spread of about milliseconds for lead-tellurium alone. Aluminum, silicon, sulfur and phosphorus function similarly to magnesium in the reduction of average burning time, and spread in accordance with this invention.

The following data illustrate firing time that can be tained with a lead-tellurium mixture of this invention as-a detonation composition in a short delay cap, there being no separate delay charge present. The base charge and primer compositions employed were pentaerythritol tetranitrate and diazodinitrophenol respectively, in conventional proportions. The lead-tellurium proportions were 6l.9/38.1 in each case.

l Stoiehiometric proportions (Gm/38.1) in, Standard 25 caliber shell.

The following tabulation of data are illustrative of firing times obtained with lead-tellurium compositions of this invention as ignition mixtures in a delay cap containing a delay fuse.

Table III Summary of Firing Times No. of Fuse (milliseconds) Ignition Mixture Fuse Powder Tests Length,

Inches Avg. Range Spread BaOg-Te(70-30)/PbSr|.' 50!60 10 0.192 470 420-1, 000 580 BaO:Te(70-80)/Pb$n, 50/50.-.- l 0. 3 770 700-1, 950 1, 250

Pb-Te I Pb-Se /BaOg-Se(82l8); 70/30 L--- 368 280-600 220 1 Stoiehiometrle proportions (6l.9/38.1), 12/64 inch length in standard caliber shell.

1 Stoichlometrie proportions (72.4/2745). I Pb/Sn (85/15). 4 (Pressed charge, 0.7 gm.)

The following tabulation illustrates elfect of magnesium and silicon on fuse ignitability in a delay cap, the tests having been conducted at -70 F. At that temperature the lead-tellurium mixture without additives burned but failed to light the fuse. As shown, 50 tests made with magnesium in the lead-tellurium mixture and tests made with silicon in the lead-tellurium mixture all shot at -70 F. At room temperature, all tests made with silicon in the lead-tellurium mixture, shot. Aluminum, phosphorus and sulfur additive function similarly to silicon and magnesium, in accordance with this invention to improve fuse ignitability.

Ignition mixture burned but failed to light fuse.

Upside down firing. p

The delay fuse in all three tests was of conventional gasless type, basically BaO- Se. The relative proportions of lead and tellurium in all cases were 61.9/ 38.1, 0.65 gram having been fired in each instance.

The presence of additives provides, as illustrated, for regulation of firing time of the lead-tellurium compositions of this invention over abroad range, lead-tellurium mixtures without additives providing an exceptionally long burning period and in that form exhibiting especial utility as a combination delay and ignition composition making a separate delay fuse unnecessary.

The compositions of this invention will burn without the production of any substantial amount of gas and thus will not rupture the cap casing or dislodge the bridgewire upon firing. In preparing a composition of this invention in accordance with one embodiment, the ingredients are reduced to a finely-divided form and are then intimately admixed by any suitable procedure. Generally the average particle size of the resulting composition will be in the range of about 1 to 70 microns, although a particle size outside that range can be utilized if desired. The composition is loaded into any desired form of blasting cap in any usual manner. No air space is required in the cap since the composition develops practically no gas on burning.

As illustrative, the composition may be loaded loosely into any form of ventless delay cap assembly above the fuse and the usual sulfur plug holding the usual bridgewire placed above the loosely loaded composition with the bridgewire embedded in the composition. Similarly, a composition may be looselyloaded into any ordinary blasting cap above the priming charge. v

the scope of the claims.

What I claim and desire to protect by Letters Patent is:

1. As a new blasting initiator composition a finely divided ignition mixture of lead and tellurium.

2. A composition of claim 1 containing a sufficient amount of at least one additive selected from the group consisting of magnesium, aluminum, silicon, sulfur and phosphorus to decrease the burning time of said composition.

3. As a new blasting initiator composition, a finely divided mixture consisting essentially of from 35 to 81 weight per cent lead and 19 to weight percent tellurium and containing from about 0.3 to 4.5 weight percent of at least one additive selected from the group consisting of magnesium, aluminum, silicon, sulfur and phosphorus.

4. A composition of claim 3 wherein said lead and tellurium are present in substantially a lead/tellurium weight ratio of 61.9/38.1.

5. A composition of claim 3 wherein said additive is aluminum.

6. A composition of claim 3 wherein said additive is silicon.

7. A composition of claim 3 wherein said additive is magnesium.

8. A composition of claim 3 wherein said additive is phosphorus.

9. A composition of claim 3 wherein said additive is sulfur.

10. A composition of claim 3 having an average particle size within a range of about 1 to microns.

11. As a new blasting initiator composition, a finely divided ignition mixture consisting essentially of from 35 0t 81 weight percent lead and from 19 to 65 weight percent tellurium.

12. As a new blasting initiator composition, a finely divided ignition mixture consisting essentially of lead and tellurium and as an additive component at least one additive selected from the group consisting of magnesium, aluminum, silicon,- sulfur and phosphorus in an amount sufficient to reduce the burning time of said composition.

13. In an electric blasting cap containing a detonatable base charge and a primer charge for initiating said base charge upon being heated, and an ignition charge for generation of heat, from burning of same, to cause initiation of said primer, the improvement providing, as said ignition charge, an ignition mixture of finely divided lead and tellurium.

14. A blasting cap of claim 13 wherein said ignition charge contains at least one additive selected from the group consisting of magnesium, aluminum, silicon, sulfur and phosphorus in an amount suflicient to decrease burning time of said ignition charge.

15. A blasting cap of claim 13 wherein said ignition charge consists essentially of from 35-81 weight percent lead and from 19-65 weight percent tellurium.

16. A blasting cap of claim 14 wherein said ignition mixture consists essentially of from 35-81 weight percent lead, from 19-65 Weight percent tellurium and contains from about 0.3 to 4.5 weight percent of at least one additive selected from the group consisting of magnesium, aluminum, silicon, sulfur and phosphorus.

17. A blasting cap of claim 16 containing a separate delay fuse intermediate said ignition charge and said primer and in operative relationship with said ignition charge and said primer so as to be ignitable by heat from burning of said ignition mixture and to thereby cause initiation of said primer.

18. In an electric blasting cap containing a detonatable base charge and a primer charge for initiating said base charge upon being heated, and an ignition mixture as the only charge for generation of heat, from burning of same, to cause intiation of said primer, the improvement providing, as said ignition charge, an ignition mixture of finely divided lead and tellurium.

19. A blasting cap of claim 13 containing a separate delay fuse intermediate said ignition charge and said primer and in operative relationship with said ignition charge and said primer so as to be ignitable by heat from burning of said ignition mixture and to thereby cause initiation of said primer.

References Cited in the file of this patent UNITED STATES PATENTS Re. 19,661 Nash July 30, 1935 2,370,159 Hanley Feb. 27, 1935 2,607,672 Spaeth et a1. Aug. 19, 1952 2,811,571 Fritts et al. Oct. 29, 1957 OTHER REFERENCES Hackhs Chemical Dictionary (1950), page 834. 

12. AS A NEW BLASTING INITIATOR COMPOSITION, A FINELY DIVIDED IGNITION MIXTURE CONSISTING ESSENTIALLY OF LEAD AND TELLURIUM AND AS AN ADDITIVE COMPONENT AT LEAST ONE ADDITIVE SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM, ALUMINUM, SILICON, SULFUR AND PHOSPHORUS IN AN AMOUNT SUFFICIENT TO REDUCE THE BURNING TIME OF SAID COMPOSITION. 